Individuals often wear goggles to protect their eyes or to improve their vision when participating in a sport or a recreational activity, such as skiing or motorcycle racing. FIGS. 1 and 4 show a typical goggle 10 of the prior art when worn in conjunction with a protective helmet 12. The goggle 10 has a frame 14, a lens structure 16, and a strap (not shown). The frame 14 encircles both of the wearer's eyes, rests on or above the wearer's nose, and has a generally horizontal section running across the wearer's forehead. The frame 14 has an inner section 15 that rests against the wearer's face, and an outer section 17 adapted to hold the lens structure 16. The inner section 15 of the frame 14 can be conformed to rest closely against the wearer's face, and can be lined with a cushion 19 to make it more comfortable. The outer section 17 of the frame 14 is formed with a groove 21 to receive the perimeter of the lens structure 16.
The lens structure 16 of the goggle 10 typically has a thin perimeter edge that is retained within the groove 21 in the outer section 17 of the frame 14. The lens structure 17, which may be single- or double-pane, is separated from the wearer's face by the thickness of the frame 14. A chamber of air is formed in the space within the frame 14 that lies between the lens structure 16 and the wearer's face.
The strap holds the goggle 10 in place on the wearer's head. The strap is typically made from an elastic material, and can be adjustable to fit a variety of individuals.
When an individual first puts on the goggle 10, the air within the chamber is the same temperature, and has the same relative humidity, as the air surrounding the goggle 10. Under these conditions, the lens structure 16 is transparent and the wearer can perform the sport or activity with full vision.
As time passes, moisture evaporating from the wearer's face increases the relative humidity of the air in the chamber. As the relative humidity increases, so does the dew point, or the point at which water molecules will condense from a vapor phase to a liquid phase. When cold air surrounding the goggle 10 reduces the temperature of the lens structure 16 to a temperature below the dew point, water will condense on the inner surface of the lens structure 16. The condensate on the inner surface of the lens structure 16 decreases the wearer's vision and makes it more difficult, or impossible, for the wearer to participate in the sport or activity.
Over the last few decades, numerous modifications and innovations have been developed with mixed success in an attempt to solve the problem of fogging goggles. These include: providing passive air vents in the frame to allow fresh air to circulate into the chamber; providing fans or the like to force fresh air into the chamber (not shown); providing double-paned lenses to insulate the internal surface of the lens structure from the cold, external temperature (not shown); and wiping the lens structure with "no fog" cloths carrying chemicals designed to prevent dew formation (not shown).
The "no fog" cloth only lasts for a short period of time before the chemical is dispersed or evaporates and the cloth must be replaced. If the cloth is used after the chemical has run out, it is no better than a shirt sleeve for the temporary fix of wiping off the fog. Even worse, the cloth is often lost or misplaced before the chemical runs out. The cloth is therefore a burden, and can become expensive if numerous replacements are purchased.
The forced air fans are an expensive addition to a goggle, significantly increasing its retail price. In addition, the fan, motor and batteries are heavy and can make the goggle uncomfortable. Also, when the batteries run out, the fan unit is worthless.
Double-paned lenses may delay the problem of fogging, but if the outside temperature is low enough, the internal lens will eventually drop to a temperature below the dew point. The colder weather, the faster the change. Consequently, if the weather is extremely cold, the double-paned lenses have substantially the same problem as single-paned lenses.
The simple, passively vented goggles 10 have proven to be a decent solution, but are problematic as well. This type of goggle 10 typically operates by having a number of vents 22 around the perimeter of the goggle 10. If the wearer is participating in an activity that entails high speeds, such as skiing, snowboarding, cycling, motorcycling, snowmobiling, etc., the air moving past the wearer's face can enter the goggle 10 through one or more of the vents 22, replacing the moist air in the chamber with less humid, outside air.
The primary problem with these types of goggles 10 is that the shape of the frame 14 is not conducive to air flow through the vents 22. Ventilated goggles 10 usually have vents 22 along their top edge 18 and bottom edge (not shown). In order to keep these edges from blocking or overly reducing the field of view of the wearer, however, these edges are generally oriented parallel to the direction of sight, which usually corresponds to the direction of travel. Consequently, if a wearer is looking straight forward, all of the vents 22 along the edges of the goggle are facing in a direction roughly normal to the direction of the air flow. This orientation is the least likely to allow for circulation of air.
In addition, the top edge 18 of most goggles 10 is slightly curved in a convex-up direction with respect to the orientation of use of the goggle 10. This has become the shape of substantially every goggle 10 on the market due presumably to the demands of appearance and ease of manufacturing. Ironically, this common curvature may lessen the air flow through the vents 22. If the wearer is looking slightly downward, which is the most common head orientation in all of the above-listed activities, the convex curvature of the top edge 18 on the goggle 10 may direct the air flow around the sides of the goggle 10. This further decreases ventilation in the goggle 10.
These problems are exacerbated when the individual is also wearing a protective helmet 12. The top edge 18 runs in a substantially horizontal direction across the forehead of the individual wearing the goggle 10. The top edge 18 is thus roughly parallel to an adjacent front edge 20 on the protective helmet 12. The gap between the top edge 18 and the front edge 20 is too narrow for a sufficient amount of air to flow through and ventilate the goggle 10. Consequently, air rushing past the wearer's face is forced either over the top of the individual's head or around the sides of the protective helmet 12.
A need therefore exists for an improved sport goggle with increased ventilation to reduce lens fogging during use, particularly when the goggle is worn in conjunction with a protective helmet.